Field of the Invention
The present invention relates to a shape of blades and struts of a wind turbine for a vertical-axis wind power generator.
Description of the Background Art
As described on page 74 of “Book On Wind Power Generation” authored by Izumi Ushiyama, a wind turbine does not rotate under a wind speed of approximately 2 m/s or lower unless the width of blades is set to be larger, for example. A wind speed at which a wind turbine starts rotating is called the starting speed or the start speed, and a wind speed at which the wind turbine starts generating power is called the cut-in speed. Due to the destruction of the Fukushima nuclear power station caused by the Tohoku earthquake disaster, the safety of the nuclear power generation has decreased, and it has been desirable to improve the efficiency of a power generator using renewable energy.
Examples of vertical-axis wind turbines are disclosed in Patent Document 1 and the like. The Document discloses a Savonius wind turbine having a simple structure capable of generating high torque at a low rotation speed without sacrificing the advantageous features of the Savonius wind turbine. According to this Savonius wind turbine, the blades have such a structure that each of the blades is curved stepwise in an inverted Z-shape or a Z-shape at a position closer to an outer end of the blade so that a portion closer to the outer end of the blade is relatively shifted toward a concave curved surface receiving wind. According to such a structure, the wind power received by an outer surface of a step plate assists the wind power received by the concave curved surface. As a result, the wind turbine generates high torque at a low rotation speed.